Which statement defines a mediator?

Which statement defines a mediator?

• A. It is a variable that moderates the strength of the relationship depending on another factor.
• B. It is a variable that reduces the size and/or direction of the relationship between a predictor and an outcome, and is associated with both.
• C. It is a variable that is unrelated to both predictor and outcome.
• D. It is a variable that is identical to the predictor.

Answer: (B)

A mediator explains the process by which a predictor influences an outcome. In mediation, the predictor X affects a mediator M, which in turn affects the outcome Y. Because M carries part of the effect from X to Y, including M in the analysis typically reduces the direct relationship between X and Y. If the direct link shrinks substantially, that indicates mediation; if it becomes non-significant, it can be full mediation. A mediator must relate to both X and Y and serves to transmit the effect from X to Y. This differs from a moderator, which changes the strength or direction of the X–Y relationship depending on the level of another variable, rather than explaining the mechanism. The other options describe a variable unrelated to both X and Y, or a variable identical to the predictor, which do not capture the mediating role.

A mediator explains the process by which a predictor influences an outcome. In mediation, the predictor X affects a mediator M, which in turn affects the outcome Y. Because M carries part of the effect from X to Y, including M in the analysis typically reduces the direct relationship between X and Y. If the direct link shrinks substantially, that indicates mediation; if it becomes non-significant, it can be full mediation. A mediator must relate to both X and Y and serves to transmit the effect from X to Y.

This differs from a moderator, which changes the strength or direction of the X–Y relationship depending on the level of another variable, rather than explaining the mechanism. The other options describe a variable unrelated to both X and Y, or a variable identical to the predictor, which do not capture the mediating role.